All you need to do is open up the flipper, detach the top grate from the bottom, and flip it over so it forms a triangle. If you're having trouble, Jonny offers a little trick to help out:

To fold the handles in, plant your foot on the grille itself to get some leverage. It might also be helpful to attach a hook to the grille to keep your laptop from sliding off (I did that later).

That's all it takes. It's only $2.75, and will keep your laptop from overheating, especially on cushier surfaces. Not to mention you can use the space between the grates to store your cables so they aren't strewn all over your desk.